I called Vandersteen Audio with the same concern and got a response very similar to what Flrnlamb said, but the only downside to not putting it on carpet mentioned was the possibility that the speaker would be more capabale of movement ("microvibrations") if not solidly tied to the floor by spikes.
If you put in a platform that the speaker can get a real good bite on, and the system is very well anchored by weight as Nsgarch suggested, seems like it shouldn't degrade the sound.
If you put in a platform that the speaker can get a real good bite on, and the system is very well anchored by weight as Nsgarch suggested, seems like it shouldn't degrade the sound.